(1) Field of the Invention
The present invention relates to an electron beam-curable composition for a release material and also to a process for preparing a release material from this composition.
The release material obtained from the composition of the present invention gives a release property, for example, to a base surface of a sticker or seal or to a back surface of a wound packaging tape.
(2) Description of the Related Art
In order to impart a release property to the surface of a release paper used as the base of an adhesive tape of a sticker or seal or to the back surface of a wound packaging adhesive tape, a method has been adopted in which an expensive reactive silicone is coated on the polyolefin-laminated base surface and a thermosetting treatment is carried out.
However, an apparatus having a length of scores of meters is necessary for the steps of coating the silicone and carrying out the heat treatment. Furthermore, since a solvent such as toluene is used at the step of coating the reactive silicone, large equipment cost and energy are necessary for recovering the solvent. As means for eliminating this disadvantage, a method may be considered in which the silicone is incorporated into a thermoplastic resin, whereby the large-scale step can be omitted. This method, however, has problems in that the release property required for the release paper is not manifested, and the silicone bleeding to the surface migrates to the adhesive layer of a sticker or seal to reduce the adhesive force of the adhesive layer.
As means for solving the above-mentioned problem, a method has been proposed in which a radiation-curable reactive organopolysiloxane is incorporated into a resin, the resulting composition is shaped by the lamination or inflation method and the shaped composition is irradiated with radioactive rays (see Japanese Unexamined Patent Publication No. 57-187221 and Japanese Unexamined Patent Publication No. 62-85930). According to this method, however, an expensive organosiloxane containing a mercapto group, a vinyl group and the like must be used, and if shaping is carried out at a high temperature, during the shaping step, the organopolysiloxane is reacted with a polyolefin type thermoplastic resin as the matrix or molecules of the organopolysiloxane are reacted with each other, with the result that the orgnaopolysiloxane is hardly caused to bleed to the surface of the shaped body and no substantial release property is manifested.
We previously developed a process for preparing a release material by incorporating a dimethylpolysiloxane in a polyolefin type thermoplastic resin, shaping the composition and irradiating the shaped composition with electron beams (see Japanese Unexamined Patent Publication No. 63-248834 and Japanese Unexamined Patent Publication No. 63-249627). However, this process has a problem in that the control of the release property is difficult and the long-period stability of the release property is not satisfactory.